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Abstract

Abstract—Two hundred thirty-seven newly diagnosed yet untreated hypertensive men and women, 35 to 54 years of age, were compared with an age- and gender-stratified random population sample of 146 normotensive men and women to find out whether psychological distress symptoms, anger expression, and alexithymia are associated with elevated blood pressure and whether the possible associations are independent of sodium and alcohol intake, body mass index, and physical fitness. The independent attributes of mean arterial pressure were studied by multivariate regression analyses after combining the subjects in the hypertensive and control groups. Three questionnaires were used: the Brief Symptom Inventory (BSI-37), a 31-item version of the Spielberger State-Trait Anger Expression Inventory (STAXI), and the Toronto Alexithymia Scale (TAS-26). Total scores of the TAS-26 were higher (P<0.001) in hypertensive men and women than in their normotensive control subjects (75.6±7.8 vs 64.1±9.8 in men and 72.9±7.1 vs 57.5±11.5 in women). There were no differences between the study and control groups in psychological distress symptoms, including anxiety, depression, and hostility, or in anger expression. In multivariate regression analyses, higher age, male gender, higher sodium intake, lower physical fitness, and alexithymia were independently and highly significantly (P<0.01 for male gender, P<0.0001 for other variables) associated with increased blood pressure, explaining altogether 39.5% of the cross-sectional variation in mean arterial pressure. We conclude that alexithymia, that is, poor ability to experience and express emotions, is associated with elevated blood pressure independent of sodium and alcohol intake, body mass index, and physical fitness.

Psychological factors can raise blood pressure acutely, but whether they lead to development of essential hypertension, as stated by Alexander1 in his early psychosomatic hypothesis, is not known. The hypothesis has been addressed in many cross-sectional studies and in a small number of prospective studies. Suppressed feelings, anger and hostility,2345 alexithymia,6 anxiety,45789 depression,9 job strain,10 stressful work conditions,11 and psychosocial stress1213 are the most common factors associated with elevated blood pressure. Some studies on suppressed hostility35 and increased anxiety14 as possible psychosomatic mechanisms in hypertension suggest that they may have a role in the development of mild high-renin essential hypertension. Prospective studies support the view that suppressed feelings2 and especially suppressed anger5 are of importance in predicting blood pressure rise with age, whereas others do not find any association between anger behavior and change in blood pressure over time.47815 Several studies suggest that high anxiety levels predict later incidence of hypertension, at least in subgroups of subjects,5789 whereas negative findings have also been reported.4 A 30-year follow-up study suggests that lack of psychosocial stress may prevent blood pressure rise with age.13

Environmental factors play a significant role in the development of essential hypertension. High sodium and alcohol intakes and obesity are associated with blood pressure rise with age.161718 Physically fit persons have lower incidence of hypertension when compared with less fit persons.1920 Low level of education is related to higher blood pressure.21 The relation is largely explained by lifestyle factors.21 However, surprisingly little is known about the possible interactions between psychological factors, lifestyle factors, and blood pressure.

We compared newly diagnosed yet untreated, moderately to severely hypertensive subjects with a population sample of men and women of matching age to find out if anger expression, anxiety, hostility, depression, or alexithymia, that is, poor ability to experience and express emotions, are associated with hypertension. Moreover, we wanted to study if the possible associations are independent or partly mediated by lifestyle factors.

Methods

Subjects

Newly diagnosed yet untreated, moderately to severely hypertensive men and women, 35 to 54 years of age, residing in the city of Turku and 3 neighboring municipalities (a population of ≈200 000 inhabitants) in southwestern Finland, were recruited into the study. The inclusion criteria were a systolic or a diastolic blood pressure consistently in the range of 180 to 220 mm Hg or 100 to 120 mm Hg, respectively, as measured within the primary health care. Patients with coronary artery disease, cerebrovascular disease, insulin-treated diabetes mellitus, or hemodynamically significant valvular disease were excluded from the study. Two hundred thirty-seven out of 252 subjects met the inclusion criteria. For a control group, a random sample of men and women residing in the same area was drawn from the national population register. For stratification, 45 subjects of each gender and each 10-year age group (35 to 44 and 45 to 54) were chosen. Subjects with antihypertensive medication or a systolic or a diastolic blood pressure of ≥140 mm Hg or 90 mm Hg, respectively, were excluded from the control group. Sixty-eight out of 83 men and 78 out of 91 women met the inclusion criteria. The study was conducted following the Second Declaration of Helsinki and was approved by the ethical committee of the Social Insurance Institution of Finland. All subjects gave their informed consent.

Examinations and Measurements

Blood pressure was measured by a trained nurse. It was recorded in seated posture with a mercury sphygmomanometer, always between 8 and 10 am, according to the guidelines of the American Society of Hypertension.22 A cuff with a bladder width of 15 cm was used. Subjects were requested to refrain from heavy exercise in the morning and to avoid cola drinks, coffee, tea, and smoking for at least 1 hour before the measurement. Blood pressure was averaged over duplicate measures obtained in 4 separate sessions within 3 weeks. Body weight was measured in light clothing without shoes with an accuracy of 0.1 kg and height with an accuracy of 1 cm. Twenty-four-hour urine samples were collected to determine sodium and creatinine excretions. Sodium was analyzed by emission flame photometry and creatinine by the Jaffé method. A 24-hour urine collection was accepted as complete if its creatinine content was >7.8 mmol for men and >6.9 mmol for women. These were the 2.5 percentile values of the 24-hour urinary creatinine of the 100 men and 100 women who had participated in the Intersalt study16 in Turku. Altogether 97.1% of urine collections in men and 90.4% of urine collections in women were complete according to these criteria. Seven-day alcohol intake was assessed by means of a questionnaire. The alcoholic drinks were converted to grams of absolute ethanol. Maximal oxygen uptake (L · kg−1 · min−1) was estimated indirectly by means of an incremental cycle exercise test.23

Three self-report questionnaires were used to assess the psychological factors: the Brief Symptom Inventory (BSI-37),24 the shortened 31-item version of the Spielberger State-Trait Anger Expression Inventory (STAXI), and the Toronto Alexithymia Scale (TAS-26).2526 The BSI-37 is a shortened version of the original 53-item BSI,27 which has been shown to have acceptable reliability in psychiatric patients and in general populations as a global measure of psychological distress. The BSI-37, which has been validated in a Finnish population study,24 does not cover psychotic symptoms. We used the general severity index, that is, the total score of the BSI-37 (range 0 to 148), as an indicator of psychological distress. The BSI-37 also gives symptom dimensions for somatization, depression, anxiety, hostility, and phobicity. A shortened Finnish translation of the original 44-item STAXI28 has been validated in a Finnish twin study.29 The 31-item STAXI assesses the intensity of feelings of anger (state anger) by 7 items, the disposition to experience anger (trait anger) by 6 items, behaviorally expressed anger (anger out) by 6 items, suppressed anger (anger in) by 6 items, and self-control of anger behavior (anger control) by 6 items. The 26-item TAS published in the mid-1980s is a psychometrically well-validated and reliable instrument for the assessment of alexithymia.252630 It is clustered into 4 factors: difficulty in identifying and distinguishing between feelings and bodily sensations (Factor 1); difficulty in describing feelings (Factor 2); reduced daydreaming (Factor 3); and externally oriented thinking (Factor 4). The TAS-26 used in our study has been translated into Finnish and retranslated into English. The accuracy of the retranslation has been checked by a native speaker of English with academic education. The Finnish translation of the TAS-26 has been validated in a Finnish population study.31 We used the total score of the TAS-26 (range 26 to 130) as an indicator of alexithymia. To assess the prevalence of alexithymia, the TAS-26 total scores were categorized according to the clinically evaluated cutoff points suggested by the Toronto group: total score of ≥74 points indicates alexithymia and ≤64 points indicates that no alexithymia is present.26

Statistics

The values are given as mean±SD. Statistical analysis of the data were performed with SAS computer programs (SAS Institute). Group mean values were compared by a 2-way ANOVA grouped on gender and disease status. If significant, Tukey’s studentized range test was used for within-gender comparisons of normotensives and hypertensives. The test gives significancies only on the level of <0.05. Correlation and regression analyses were performed after combining the subjects in the hypertensive and control groups. Associations between the studied variables were tested by calculating bivariate Pearson’s product moment coefficients and gender-, age-, and gender/age-adjusted partial correlation coefficients. To find out independent correlates of blood pressure and predictors of alexithymia, multiple linear regression analyses were made by use of the statistically significant (P<0.05) correlates. Before the analyses, a variable with skewed distribution (alcohol intake) was moved closer to normality by use of its natural logarithm.

Results

Demographic and Lifestyle Characteristics

Hypertensive and normotensive subjects did not differ in their socioeconomic status (Table 1⇓). As compared with their normotensive control subjects, hypertensive men and women were slightly older, had higher relative body weights and 24-hour urinary sodium excretions, and slightly lower maximal oxygen uptakes (Table 1⇓). There were fewer smokers among hypertensive than among normotensive men and women (Table 1⇓). Hypertensive and normotensive subjects consumed alcohol in equal amounts (Table 1⇓).

Psychological Characteristics and Symptoms

The mean of total scores of the TAS-26 was higher (P<0.001) in hypertensive men and women than in their control subjects (Table 2⇓). Hypertensive subjects had more (P<0.001) difficulties in identifying (TAS-26 Factor 1) and describing (TAS-26 Factor 2) feelings, more (P<0.001) of externally oriented thinking (TAS-26 Factor 4), and slightly less (P<0.05) daydreaming (TAS-26 Factor 3). In comparison with their normotensive control subjects, hypertensive men and women were differently (P<0.001) distributed in the 3 TAS-26 score categories. Prevalence of alexithymia was higher among hypertensive men (57%) and women (46%) than among normotensive men (18%) and women (9%). Only 4% of hypertensive men and 5% of hypertensive women but 54% of normotensive men and 73% of normotensive women were nonalexithymic.

There were no differences between the study and control groups in state-anger, trait-anger, anger-out, anger-in, and anger-control behavior (Table 3⇓). Hypertensive women had more somatization symptoms than did normotensive women (Table 3⇓). The study and control groups did not differ in depression, anxiety, hostility, or phobicity or in the general severity index of the BSI-37.

Correlates of Blood Pressure in Multivariate Analyses

In multivariate analyses with statistically significant gender-adjusted correlates of mean arterial pressure, 39.5% of the variation in mean arterial pressure was explained by age, gender (female 0, male 1), 24-hour urine sodium, maximal oxygen uptake, and total score of the TAS-26 (Table 4⇓). In a model in which total score of the TAS-26 was not included, 25.2% of the variation in mean arterial pressure was explained by age (P<0.0001), gender (P<0.05), body mass index (P<0.0001), and 24-hour urine sodium (P<0.0001).

Independent Correlates of Blood Pressure Based on Multiple Regression Analyses

Demographic and Lifestyle Correlates of Alexithymia in Univariate and Multivariate Analyses

Total score of the TAS-26 correlated positively with age (R=0.12, P<0.05), body mass index (R=0.25, P<0.001), alcohol intake (R=0.13, P<0.01), and 24-hour urine sodium level (R=0.20, P<0.001). The inverse association of total score of the TAS-26 with maximal oxygen uptake became significant (R=−0.16, P<0.01), and the association with alcohol intake disappeared after adjustment for gender. In multivariate analyses with gender, age, and lifestyle factors, 11.4% of the variation in the total score of alexithymia was explained by gender (P<0.0001) and body mass index (P<0.0001).

Discussion

Our study showed that alexithymia, that is, poor ability to experience and express emotions and proneness to externally oriented thinking, differentiates men and women with untreated hypertension from their normotensive control subjects, whereas anger expression (including suppressed anger) or psychological distress symptoms (including anxiety, depression, and hostility) do not. Hypertensive women had more somatization (bodily sensations) than did normotensive women. In accordance with earlier studies, higher age,16 male gender,3233 higher sodium intake,16 and lower physical fitness1920 were associated with elevated blood pressure. Almost 40% of the cross-sectional variation in mean arterial pressure was attributed to age, gender, sodium intake, physical fitness, and alexithymia. Age, gender, and lifestyle factors alone explained ≈25% of the variation in mean arterial pressure. A relatively small portion of the association between blood pressure and alexithymia was mediated by lifestyle factors, mainly by higher relative body weight.

Psychological distress symptoms may fluctuate with time.34 On the contrary, alexithymia is generally considered as a stable personality trait.313435 A recent population study showed that alexithymia is associated with male gender, low educational level, low socioeconomic status, and weakly associated with advanced age.36 In our study, normotensive men were alexithymic twice as often as normotensive women, but the difference in alexithymic personality features was small between hypertensive men and women. Our normotensive and hypertensive subjects were practically of matching age and had a similar socioeconomic status. Hypertensive men and women had no signs and symptoms of coexisting cardiovascular diseases. Thus factors other than age, socioeconomic status, and coexisting diseases explain the high prevalence of alexithymia observed in our hypertensive subjects.

Because of the cross-sectional nature of our study, we cannot draw any conclusions concerning the causality of the relations between alexithymia and essential hypertension. Our hypertensive and normotensive subjects did not report differences in psychological distress symptoms, which suggests that alexithymia hardly is a reaction to the awareness of having elevated blood pressure.

Theories of the causes of alexithymia range from neurobiological to sociocultural ones. Neurobiological theories suggest that alexithymia may be related to an interruption of the limbic-neocortical communication, may be a result of a deficit in interhemispheric communication, or may be a result of a dysfunction in the right cerebral hemisphere.3537 Psychological theories suggest that growing up in an emotionally poor and unstimulating environment or that a massive psychological trauma later in life could result in alexithymia.38 Recently, it has been suggested that alexithymia, regardless of its cause, reflects a deficit in cognitive processing and regulation of emotions.35 Poor ability to be aware of and to cope with emotions may make an alexithymic individual vulnerable to continuous stress.

Our study group consisted of untreated hypertensive patients and the control group of a random population sample of healthy men and women, all 35 to 54 years of age. To ensure that the sample of hypertensive patients would represent normal clinical settings, all local primary care physicians were requested to send patients with uncomplicated yet untreated sustained hypertension to the study. The ratio of hypertensive men to hypertensive women was 1.4, corresponding to the national ratio of hypertensive men and women of the same age.32 The random sample can be considered representative of the target population because the participation rate was >80%.39 Blood pressure was measured carefully by a trained nurse and averaged over 4 duplicate measures. We have earlier shown that this technique is as reliable as ambulatory blood pressure monitoring in assessment of an individual’s blood pressure status.40 It also gives considerably lower blood pressure values compared with the usual measurements made by nurses or physicians within the primary health care.40 According to the carefully controlled repeated blood pressure measurements, only 20% of our hypertensives had a moderate and 5% a severe hypertension.40 A single, carefully conducted 24-hour urine collection was used for estimation of sodium intake. More than 90% of the urine collections were determined to be complete. Our study may still underestimate the association of dietary sodium with blood pressure, mostly because of the known large intraindividual variability in daily sodium intake, compared with smaller interindividual differences.4142

In summary, alexithymia, that is, poor ability to experience and express emotions, is associated with elevated blood pressure independent of sodium and alcohol intake, body mass index, and physical fitness. Prospective studies measuring alexithymic personality features before elevated blood pressure as well as studies dealing with the neurogenic mechanisms of alexithymia are needed to elucidate its role in the pathogenesis of essential hypertension.